1. Field of the Invention
The present invention relates to a composition for an organic polymer gate insulating layer and an Organic Thin Film Transistor (OTFT) using the same, and more particularly, to a composition for a photoreactive organic polymer gate insulating layer that can be micropatterned and an OTFT using the composition.
2. Discussion of Related Art
Due to the abundance of methods for synthesizing their materials, the ease with which they are formed and processed, their flexibility, low production cost, and so on, OTFTs made of organic material are being vigorously researched for use in various new electronic and optical devices.
OTFTs are expected to be frequently used in actuation devices of plastic-based active Organic Light Emitting Devices (OLEDs), smartcards, and plastic chips for inventory tags, and thus are currently being researched in the foremost companies, research institutes, universities, and so on. OTFT performance is evaluated in terms of field effect mobility, an on/off ratio, mobility, a subthreshold slope, and so on. In addition, OTFT performance is influenced by the degree of crystallization of an organic active layer, an electric charge characteristic of an interface between an organic insulating layer and the organic active layer, a thin film characteristic of the organic insulating layer, a carrier injection capability of an interface between source and drain electrodes and the organic active layer, and so on. To improve these characteristics, various methods are being tried out.
As a gate insulating layer of an OTFT, a material having low electrical conductivity and a high breakdown field is required. Currently, silicon oxide layers are used as gate insulating layers of OTFTs. When an inorganic insulating layer is applied to an OTFT, physical/chemical characteristics of a substrate (particularly, plastic substrates) and other layers, i.e., previously-processed layers formed on the substrate in previous processes, are affected by high temperature required to form the inorganic insulating layer, and characteristics of the OTFT may deteriorate. Therefore, research is underway into a new organic gate insulating layer that can be formed through a low-temperature process and thus minimize deterioration of previously-processed layers.
Currently, polyimide (Korean Patent Publication No. 2003-0016981), polyvinylalcohol (PVA) (Korean Patent Publication No. 2002-0084427), poly(vinyl phenol-maleimide) (Korean Patent Publication No. 2004-0028010), photoacryl, etc., are used for organic insulating layers, but do not have as good device characteristics as an inorganic insulating layer. Therefore, in order to implement a highly efficient OTFT, an organic gate insulating layer which can be formed thin through a simplified process without affecting a substrate and previously-processed layers, as well as a material for an organic active layer, must be developed.
While conducting research on an organic polymer gate insulating layer for efficiently implementing OTFTs, the present inventors uncovered the following facts upon which the present invention is based. When a composition obtained by dissolving a polymer having excellent insulation characteristics, such as polymethylmethacrylate (PMMA), PVA, polyvinylpyrrolidone (PVP), poly(vinyl phenol) (PVPh) or a copolymer thereof, a crosslinking monomer having two or more double bonds, a photoinitiator, and a thermoinitiator, in an appropriate solvent, is used as a material for gate insulating layer, it is possible to form a thin film comprising a semi-interpenetrating polymer network that can be micropatterned and improve electrical characteristics. Furthermore, when the thin film is used in an OTFT, it is possible to improve device characteristics.